1. Field of the Invention
The present invention relates to a panel or a substrate of a liquid crystal display device and, more particularly, to a panel or a substrate of an active matrix liquid crystal display device and the repairing method of the same.
2. Description of Related Art
The improvement of the yield of the process for manufacturing a panel of a liquid crystal display device (LCD) is very important. For improving the yield, it is necessary to repeatedly inspect in all the steps of the manufacturing process for screening out the unqualified products. However, particles exist inside and/or outside the apparatuses for manufacturing processes. The particles usually result in defects on the substrate for the liquid crystal display devices. For example, as a particle 90 falls on the surface of the switch 21 of the substrate 1 (see FIG. 1), the particle 90 results in shorting between the data line (source line) 35 and the drain 36. This shorting causes source-drain leakage and will further make the liquid crystal display device generate dark dots or bright dots (i.e. point defects) as the display device displays.
Since dumping the liquid crystal display device with point defects directly costs money, the manufacturers of LCD devices do many efforts on improving the manufacturing process and environment for manufacturing. For example, the LCD makers increase the frequency for cleaning the environment, enhancing the monitoring for the cleanness of the manufacturing environment, and improving the maintenance of the manufacturing apparatuses. On the other hand, the LCD manufacturers also develop method for repairing the LCD panel or the substrate of the LCD devices for saving costs. The yield can be improved effectively if the defected LCD device or the substrate of the LCD device can be well repaired. Of course, the cost can be reduced when the defected LCD device or the substrate of the LCD device can be well repaired.
The conventional method for repairing the defects on the LCD is shown in FIG. 1. A particle 90 falls on the surface of a switch (thin film transistor) 21 of a normally black liquid crystal display device and further results in a TFT defect such as source-drain leakage or TFT weak. When a voltage is applied on the LCD, a bright dot (i.e. a point defect) generates. The conventional method for repairing the defects illustrated above is achieved by welding the capacitor conductive lines 47 and the capacitor top lead 471 together and further cutting the drain 36, wherein the capacitor top lead 471 contact the pixel electrode 52 through contact holes 45, and the pixel electrode 52 electrically connected to the switch 21 through the drain 36. The cross of FIG. 1 marks 500 is the position of cutting. After repairing, the repaired pixel of the LCD acts as a permanent dark dots. Since human eyes are not sensitive to the dark dots, the consumer can also accept the LCDs with limited dark dots. Even though the tolerance value for the dark dots is higher than that of the bright dots, the permanent dark dots are not actually recovered through the conventional repairing method. In other words, the permanent dark dots are still abnormal pixels.
In addition, the defects caused by other factors decrease greatly since the process for manufacturing LCDs improves a lot in recent years. Hence, the point defects resulted from source-drain leakage become major defects relatively. Moreover, the tolerable requirement for the point defects becomes strict as the size of the LCD increases. Therefore, it is desirable to provide an improved method to mitigate the aforementioned problems of the source-drain leakage.